The present invention relates to a tilting device for a lens, and more particularly, to a tilting device for a lens using an actuator which is suitable for a floating type optical head.
As an actuator of a tilting mechanism for adjusting tracking of a pickup portion of an optical disk, a moving coil type motor using a moving coil, a permanent magnet and a magnetic material is mainly used (page 124 of xe2x80x9coptical disk techniquexe2x80x9d published by Radio Gijyutu Co.).
For example, Japanese Patent No.2719974 discloses optical pickup using a magnetodynamic device. In the magnetodynamic device of the optical pickup shown in this publication, a magnet is mounted to a lens holder which is supported by a spring such that the holder can be displaced, and a magnetic yoke and a driving coil are provided on a fixed side of the magnet such as to be opposed to the magnet. In this magnetodynamic device, when the lens holder is displaced in its movable range, a value of X=g/(bxe2x88x92a) is set such that a magnetic force applied to the lens holder is substantially proportional to the displacement distance, wherein a is a widthwise size in a direction in which the lens holder is displaced, b is a vertical size of the yoke, and g is a gap size between the magnet and the yoke.
Japanese Patent No. 2757539 discloses a tracking adjusting method of a floating type optical head using a relay lens. The floating type optical head in this publication comprises an object lens for converging laser beam into an optical disk, a slider for floating the object lens from a surface of the optical disk by a dynamic pressure air bearing effect to maintaining a distance between the object lens and the optical disk substantially constant, a movable portion which is driven along a radial direction of the optical disk by driving unit, and a stationary portion having a light source of the laser beam, detecting unit which detects a deviation amount between focusing and tracking, and focusing control unit which controls focusing based on a signal detected by the driving unit. This floating type optical head further comprises tracking control unit having a lens comprising a plurality of lenses for optically finely controlling tracking of the laser beam combined in the stationary portion, a signal separating circuit for separating signals corresponding to the deviation amount of the tracking output from the driving unit into a high frequency signal and a low frequency signal, a first drive control circuit for controlling the driving force of the driving unit based on the low frequency signal separated by the signal separating circuit, and a second drive control circuit for controlling the driving force which moves one of the relay lenses of the tracking control unit in a direction intersecting the optical axis at right angles.
Japanese Patent Application Laid-open No. 5-94628 discloses a method using a linear motor as an actuator for adjusting the tracking of the floating type optical head. An optical storing and reproducing apparatus of this publication comprises an object lens for converging laser beam into an optical disk, a slider for floating the object lens from a surface of the optical disk by a dynamic pressure air bearing effect to maintaining a distance between the object lens and the optical disk substantially constant, a movable portion which is driven along a radial direction of the optical disk by driving unit, and a stationary portion having a light source of the laser beam, detecting unit which detects a deviation amount between focusing and tracking, focusing control unit which controls focusing based on a signal detected by the driving unit, and tracking control unit which controls tracking based on a signal detected by the driving unit. This floating type optical head further comprises a lens for controlling the tracking by moving the lens in a direction intersecting the optical axis at right angles, this tracking control lens is supported by a resilient support member having high rigidity such that the lens can move in a direction intersecting the optical axis at right angles.
However, any of the moving coil-type actuator, the relay lens and the linear motor is heavy and is not suitable for the floating type optical head. Further, there is a problem that since the weight is heavy, an inertial force is great and a tilting motion of the lens for correcting the tracking at high speed can not be adjusted at high speed. Further, since a structure of the actuator itself is complicated, it is complicated to mount the head and assemble the same.
It is an object of the invention to provide a tilting device for a lens using an actuator which is suitable for a floating type optical head and which has a light and simple structure.
A first aspect of the present invention provides a tilting device for a lens for tilting a lens formed of optical material, comprising a plurality of beams for supporting the lens, and electrostatic force applying unit which applies electrostatic force to the plurality of beams, wherein the electrostatic force is applied to the plurality of beams to bend the beam, thereby tilting the lens. According to this aspect, the plurality of beams support the lens, the electrostatic force applying unit applies the electrostatic force to the plurality of beams, the electrostatic force applied to the plurality of beams tilts the lens, thereby changing the angle of the lens.
A second aspect of the present invention provides a tilting device for a lens according to the first aspect, wherein the number of the plurality of beams is three or more. According to this aspect, three or more beams are formed.
A third aspect of the present invention provides a tilting device for a lens according to the first or the second aspect, wherein the plurality of beams are formed helically. According to this aspect, the plurality of beams are formed helically.
A fourth aspect of the present invention provides a tilting device for a lens according to any one of the first to third aspects, wherein a portion of each of the plurality of beams is that supports the lens is formed narrower. According to this aspect, the portion of each of the plurality of beams is that supports the lens is formed narrower.
A fifth aspect of the present invention provides a tilting device for a lens according to any one of the first to fourth aspects, wherein a portion of each of the plurality of beams is that supports the lens is formed thinner. According to this aspect, the portion of each of the plurality of beams is that supports the lens is formed thinner.
A sixth aspect of the present invention provides a tilting device for a lens according to any one of the first to fifth aspects, wherein the electrostatic force applying unit comprises a first electrode formed on each the beam, a second electrode formed at a location opposed to each the beams through a gap, and voltage applying unit which applies voltage between the first electrode formed on the beam and the second electrode to apply the electrostatic force to the beam. According to this aspect, voltage applying unit applies voltage between the first electrode formed on the beam and the second electrode formed such as to be opposed to the first electrode through a gap to apply the electrostatic force to the beam.
A seventh aspect of the present invention provides a tilting device for a lens according to the sixth aspect, wherein the gaps are not parallel to each other. According to this aspect, the gaps are not parallel to each other.
An eighth aspect of the present invention provides a tilting device for a lens according to any one of the first to seventh aspects, wherein the lens and the plurality of beams are made of the same material. According to this aspect, the lens and the plurality of beams are made of the same material.
A ninth aspect of the present invention provides a tilting device for a lens according to any one of the sixth to eighth aspects, wherein the lens, the plurality of beams, a first substrate formed with the first electrode and a second substrate formed with the second electrode are connected to one another. According to this aspect, the lens, the plurality of beams, a first substrate formed with the first electrode and a second substrate formed with the second electrode are connected to one another.
A tenth aspect of the present invention provides a tilting device for a lens according to the ninth aspect, wherein the second substrate is a semiconductor material. According to this aspect, the second substrate is a semiconductor material.
An eleventh aspect of the present invention provides a tilting device for a lens according to the ninth or tenth aspects, wherein the second substrate is provided with the voltage applying unit. According to this aspect, the second substrate is provided with the voltage applying unit.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.